An aircraft commonly includes a water supply system in order to provide on-board water-use stations with fresh water. Such a system can comprise a water source line capable of continuously supplying water at a supply temperature (e.g., a temperature at least warm enough to prevent freezing) and a plurality of water-use stations. Certain water-use stations, such as hand wash basins in lavatories and sinks in galleys, have a hot water line and a cold water line. The stations can each incorporate a faucet assembly which mixes the water from the hot and cold water lines for discharge through a spout. The faucet assembly can include handle/valve means to manually control the discharge time and to adjust the temperature and flow rate of the discharged water.
The hot water line of each water-use station will commonly include a local heater to heat the relatively cold water from the water supply to a hot temperature (e.g., about 45° C.). The heater heats the water at a certain heating rate (e.g., kg*ΔC°/s) dependent upon the power provided thereto. For example, a heater operating at 400 watts will take about twice as long as a heater operating at 800 watts to heat a kilogram of water a given number of temperature degrees. Likewise, a heater operating at 800 watts will heat about twice as much water as a heater operating at 400 watts in a given amount of time.
Typically, a plurality of heaters (e.g., six heaters) are grouped together and powered by a single power source. Conventionally, each heater consistently used a set amount of power (e.g., 400 watts) to heat the water thereby always heating water at a corresponding heating rate. The power source was selected (and/or the heaters were selected and/or grouped) so that enough power (e.g., 2400 watts) was available for all of the grouped heaters to be operated at the same time.